Instrument cover-glass



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C. H. COLVIN May 23, 1933. 1,910,092

INSTRUMENT COVER GLASS Filed May 20, 1929 I I i l.\'l 'L-LVTOR. CHARLES H. COLVIN V I) Y a WMQ ZM :1 T T QRNE Y5.

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JThis invention relates to cover-glasses for instrument housings and more particularly 1 parts of instruments are to be observed.

Heretofore, some cover-glasses or lenses which are used to close the open areas of housings, such as compass-bowls, have had convex exterior surfaces. 1 While this type of cover-glass is "satisfactory for reading purposes, oftentimes, a cover-glass of this type causes difliculty in observing therethrough the working parts of an instrument because the convex outer surface serves as a u a reflecting surface from which light may reflect into the eyes of an observer. On cer-' 'tain headings, especially when the sun is in the rear of the observer, the reflection is most impossible to .read the .parts of the instruments enclosed behind the coverlass. It is, therefore, among the objects 0 this invention to provide a cover-glass throu h which the interior of an instrument may 7 observed without anno ance to an observer because of reflected lig t.

' Another object of the invention'isto provide a cover-glass through which the inte- .rior of an instrument, such as a liquid como Pass, may be illuminated from a source of ight placed exteriorly of the. instrument without enabling reflection of light from the cover-glass into the eyes of an observer.

pointedout hereinafter'in the description V and claims. 7 4 a For the purpose of illustration, I have selected a compass as an example of a type of instrument with which the invention may be stood that the invention ma be used in conboards ofaircraft. In the the cover-glass in section. 1'

' g: "front elevation bf "tn to cover-glasses through which the working similar to that shown in Fig. 1 an sometimes so pronounced as to make it al-- place b .'Other objects and advantages will be advantageouslyused and i is to beviunder' .nection with other types of instrumentssuch as those commonly found on the ms'rnumrcovsn-euss application fled an no, me. ca Io. mm.

Fig. 3 is a section of thecover-glass on line 3-3 of 2. a

Fig. 4 is an ustration of a comdpass-bowl its position relative to an instrument board and exterior source of illumination.

Fig. 5 is a .front elevation of the liquid compass equipped with the cover-glass and showing the relation of the instrument board and source of illumination illustrated C in Fig. 4.

The 21 ass-bowl 10in the housing 1E? all sides 0 osed except for an open area through which the workin parts of the compass are tobe observe The present type of compass is well-known as a liquid conga-pass, a type in which the compass-bowl is led with a liquid. A compass-card 11 is mounted upon apost 12 and isfree to rotate and tilt in any direction, and a lub bers line 13 is provided for facilitating reading of the compass-card.

The open area of the compass-bowl is closed by a cover-glass 14 which is held in Though the shape of the openarea of the compass-bowl may assume various outlines, it is found convenient to y, in the orm of the invention illustrated in Fig. 2 the cover-glass has a circular out- A "line to accommodate the outline'of the'opea area of the 'co'mpass bowl.

- The cover-glass illustrated is inthe "form"" a of a convex' lens having an interior concave surface 17, and an exterior surface 'com'-- 1' posed of two convex surfaces 18,19and a transverse band 20 which is generated by a] 1,1i ne or element moving in a curved path 'parallel to a cFor the purpose ofconvenience the edge of the cover-glassis j -;in the form-of aring 21 havin 'flat sides Y iby whichthe cover-glass may clampedg Fig. 1 illustrates aside view .ofa-liquid, compass'-with a side wall broken away to I shown a'portion-of the interior thereof and I in lace by the coverglass rin 15'.

n the W cm...

b s v r i-I poeed'to-the suns raysun er condishowing 1 Y a cover-glass ring v15 suitably mounte by some such means as screws 16."

7 provide an open area havin a circular outhne. According- UNITED ST TES PATENT-L 1 CHARLES H. COLVIN, 0F BROOKLYN, NEW YORK, ABSIGNOI TQ PIOKEEB comm, INCORPORATED, 0! 330031;, NEW YORK, A CORPORATION 01' mtw s v tions and whether or not the instrument is r being observed, if reflections from the surface of its cover-glass exist, a navigator is continually annoyed. Reflections of this order often render the reading of aninstru- 'ment'painful if not altogether impossible. f Cover-glasses having exterior spherical surfaces have been used and, as may be easily understood, owin to the character 'of the exterior surface, hght rays from any source in front of or at the side of the exterior surface would strike an area from which' they would be reflected into the eyes of an observer. In takin corrective measures to avoid harassment 0 this nature I eliminate any spherical exterior surface at-the.midportion of the coverlass, and cover, as with paint or other suita le covering, the exterior portions 18, 19 above and'below the mid-portion 20. This arrangement of exterior surfaces gives a transparent mid-portion 20 which operates as a lens to give lateral magnification to the side of the compasscard and hence to the spacings between vertical direction markings on the compass. 65,111. s l As illustrated in the drawing the coverglass is so mounted in the open area of a compass-bowl as to dispose the elements of the curved surface 20 in substantially a ve rtical direction. I f As may be readily understood, any rays from the sun striking curved surface 20 may 7 not be reflected into the eyes of an observer who is positioned immediately in front of the cover-glass. All such rays would take T a path similar to that diagrammatically illustrated at 21 in Fig. 1 and would be cidenoe of the light rays 24 be greatly incaused would be the same and the observer would not be annoyed by reflections. 'Since I a non-reflecting coating,-no;trouble iscaused b'y reflection from these surfaces. h r I A very desired advantage to behad-with :L. the use of the presentinvention is illustrated 1 .with liquid the problem of illuminating the compass-card is notifanieasy. one. fHowever, with the type of cover-glass 'or' lens disclosed eyes of an observen Formakin'gguseofthis advantagethe compass-bowl-g'lfl isnmounted board which in; a ho e m w i hsft ev gle rude ke ligh -f r the insuchla pofsr as that.-.{rays ofIlight emitted thereby creased over the angle illustrated, the result; gl hieh tig-generatedjby -g, 1; igfi the convex su'rfacesglfl, 19 are coated with fall upon the surface the cover-glass and illuminate the compass-card'll and lub bers line 13. No annoyance because of reflection is caused to the observer since the"- rays of l' ht do not find an areaof the surface20 w ch is so sloped as .to reflect light from the source of light 24 into the eyes of the observer. Since the convex surface 19 is light absorbing; no reflection, will be had therefrom. In this particular'instance the convex surface 18 has no portion thereof capable of reflecting light from the source of light 24 into the eyes of the observer.

I wish it to be understood that because it is customary to refer to a transparent member closing an open area of a houslng as a cover-glass, I have used the term in like of an integral element having a plane ring at its periphery by which it may be aflixed to a housing and a protruding portion with manner herein without, however, desiring to limit myself to the kind of material used. r r A simple form of cover-glass may consist a cylindrical outer surface flanked by spherical surface portions. Since my invention is sub ect to variations in form without departure from the nature and .principle thereof I do not restrict myself unessentially in the foregoing or other particulars, but contemplate such alterations and modifications within the scope of the appended claims as may be found to be advisablep Iclaim:

side and aworkingf' 'parts tofibe robse'rved e combination with an earnest therein, said open area'jbeing circular, of a 'covemglass closing ;'.the' of nareapfsaid reflected downwardlyf nto .the cock-pit of h sing, said ,eoyer';;g1 ss::

2. The combination Wltll an instrmnent having a housingwith anopen areaionzone I V side and working parts to beobserved there in, of a lens closing the open area of said. r v housing, a said lens bein 'roundedi'outgraphlcall 1n F1gs.4 and5. OWlllg t0 the .wardly from thehousing'an ai -3115 the aircraft. Even though the angle of inh i t n ygr e id- 1m .fact'that t e interiorof th ompass ls fill d verse :b d across the midwortiomof in exterior face ich is generated by a vertical] a directrix, and a covering of non-reflecting i ni P S Q' q m f "t v-material on the outer-surface .ofthe' spherpa f t l s d z f t m -ical portion of said #lens .wh'ereby reflection without causing reflection of lightjntoi-the offexternallight is eliminated.

4 ftriiiheii v f having 'a'housingwith ani'open-area ane vposltwn a w wia th an m sideand'working' parts .to :be observedi'thereto itself and through which the workin parts within the housin may be observ and rounded outer sur aces rendered substantially non-reflecting, and a source of light for illuminating the interior of said housing, said source of light being disposed lateral y ofthe cover-glass and beyond the horizontal plane bounding either t e u per or lower limit of the curved surface de ed whereby the interior of the housing may be illuminated from said li ht source without causing reflection into t e eyes of an observer observing the working parts within the housing. a 4. The combination with an instrument having a housing with an open area on one side and working parts to be observed therein,- of a cover-glass carried by the instrument and closing the open area of said housing, said cover-glass being convex and extending beyond the plane of said open area and having a transverse portion in the form of a horizontally .curved band generated by a the movement of a vertical line parallel to a directrix whereby reflection-of external light is eliminated, a lpanel having an aperture throu h which t e cover-glass may be observ and illuminating means positioned laterall of the convex portion of said cover- -glass w ereby light may be directed into the instrument housing.

5. The combination with an instrument panel and an instrument having a housing with an ofin area on one side and working.

observed therein, of a convex 4 'parts' to cover-glass carried by the instrument and closin the open area of said housing and exten ing beyond the plane of the open area, said cover-glass having a horizontally curved transverse band across its mid-portion through which the interior of the housing may be seen and substantially non-reflecting spherical portions bordering said mid-portion, illuminating means positioned laterall of the cover-glass and rearwardly of the instrument panel whereby light may be directed through its mid-portion and into the instrument housing, said panel serving as shielding means for preventing illumination forward of the instrument.

6. The combination with an instrument in, ofa cover-glass closing the open area of V said housing, said cover-glass having an outer surface with a portion thereof in the form of a horizontally curved band enerated by the movement of a vertica line parallel to itself whereby horizontal reflection of light incident on the surface from.

above the horizontal is eliminated.

8. The combination with an instrument having a housing with an open area on one side and working parts to be observed there-' in, of a cover-glass closing the o 11. area of said housing, said cover-glass transparent horizontally curved mid-portlon avin'g a 1 through which the working parts may be observed, and non-reflecting spherical portions bordering said mid-portion.

In testimony whereof I hereto my I signature. I g CHARLES H. OOLVIN.

having a housing with an open area on one side and working 1parts to be observed therein, of means for i uminating'the interior of 55 said housing, said illuminatm disposed out side of said housmg and to one side, a cover-glass carried by said housing and closing said open area, said coverglass being rounded and protruding from the open 50 area of said housing and having a transverse portion in the form of a horizontally curved band, and a blackened non-reflecting surface covering a portion of the outer surface of the cover-glass whereby the transparent area of said cover-glass is "restricted.

ns being 

